What a confusing spring!

March weather had the rattlesnakes along the American River Parkway confused! As I have mentioned before, the rattlesnakes usually emerge and begin to bask when the average temperature at ground level remains at or above about 50F. They are usually deep enough underground during the winter to escape daily high and low fluctuations, so it is the average that eventually penetrates to them and signals that winter is likely over. But not this year.

Most telemetered rattlesnakes emerged in March but remained at their hibernation sites, basking on sunny days as they usually do before leaving their winter shelters. But rather than getting drier and warmer, the weather throughout April was a constant mixture of rain and cloudy cool days and nights. Of the few rattlesnakes that left their winter hibernacula, two returned while others became inactive at other sites. The rattlesnakes do just fine in the rain. In fact, they drink rain and dew when it’s available. And cloudy weather is not a deterrent to activity if it is accompanied by warm temperatures. But nighttime air temperatures below 50F followed by overcast cool days are not good for activity in animals like reptiles that depend on the environment for their body heat.

So, in late March and throughout April, the few stretches of several sunny days with relatively warm nights in between produced some sporadic rattlesnake activity. But it was not until the end of April that more consistent sun and heat produced vigorous widespread rattlesnake activity.

A courting pair of rattlesnakes on 28 March, next to the log under which they spent the winter. The male is on top of and mostly obscuring the female, which is paying no attention to him.

As expected, when we had activity, we observed lots of courtship. This is, after all, the peak of courtship activity, followed by almost no reproductive activity from June to mid-August before an untick in courtship again in the fall.

But by far the most interesting discovery this spring was by one of my UC California Naturalist students who found a small male rattlesnake with no rattle! (See photos below) Now I hesitate to mention this, for fear of starting a panic about rattleless rattlesnakes. Please remember several things:

  1. Rattlesnakes missing their entire rattle are extraordinarily rare. So rare, in fact, that they usually rate a note in a biological journal. This one will!
  2. No rattlesnake has a long pointed tail like our many harmless snakes.
  3. Rattles can be missing due to either injury or genetic mutation.
  4. This little snake appeared to be recently missing the end of his tail and had other serious but healing injuries. Apparently a close call with a predator!
  5. Identify rattlesnakes by looking at the tail! Yes, rattlesnakes have elliptical pupils and heat-sensitive facial pits but some harmless snakes have elliptical pupils and both these characters are too small to be clearly seen from a safe distance (two-times the length of the snake). Some harmless snakes also have rather triangular heads, especially when they have been frightened and are behaving defensively. But no rattlesnake has a long pointed tail like our harmless snakes and all of California’s dangerous snakes are rattlesnakes.

Check out the following images…

Our rattleless Male 87, on the day of his capture, 09 April 2017. He is only about two feet long. Note that his appearance is “rattlesnake” in every way except for the stump of a tail without a rattle.
Close-up of Male 87’s tail.
Dorsal x-rays of Male 87’s tail (right), compared to a normal rattlesnake’s tail (left). The large opaque “club” in the normal tail is the calcified stylus inside the tail to which the shaker muscles attach (the hollow keratinized rattle on the normal tail is present but invisible to the x-rays). Many thanks to Hazel Ridge Veterinary Clinic for the radiograph.
One of several other healing injuries on Male 87. (The scale is centimeters; 2.54 cm = 1 in)
This is a harmless but badly frightened gopher snake that has just been stepped on by a hiker. Note how it has flattened its head into a triangle. It was also vibrating its tail in the grass, producing a good imitation of a rattlesnake. But a look at its tail reveals that it is not a rattlesnake (see next photo) and, therefore, a harmless California snake.
No rattlesnake has a long pointed tail like this gopher snake.

To be sure, there are dangerous snakes in other parts of the United States that have long tails without rattles (cottonmouths, copperheads and coral snakes, in southern and eastern states). But in California and other northwestern states, the only dangerous snakes are rattlesnakes.

Look at the tail to identify rattlesnakes!

 

 

And, yes, Male 87 was processed and released, just like all the others. While he has no paint in his rattle, he won’t be hard to recognize!

5 thoughts on “What a confusing spring!”

  1. Interesting narratives, Mike. Thank you. The harmless gopher snake is a remarkable look alike to the rattle snake. How is a male rattlesnake identified in comparison to a female rattlesnake? Can the difference be seen from the safe distance of two times the length of the snake?

    1. Hi Tana!

      Distinguishing male from female rattlesnakes without handling them is neither easy nor certain. Males have longer tails that are a little wider at the base (near the body), while females have shorter tails that are narrower and not tapered. The difference in length is not much: tails average 7.4% of total body length in males but only 5.4% in females. With a lot of experience, I get it right just by looking maybe 80% of the time. I’ll post some photos to the blog for everyone to see.

      The difference is caused by the male’s copulatory organ, which is essentially a bifurcated (i.e. forked) penis in lizards and snakes. Each side is called a “hemipenis” by herpetologists (plural is “hemipenes”) and they are stored inside the tail except during copulation. The stored hemipenes are soft inverted tubes that extend more than half the length of the tail from the cloaca (the vent or anus in reptiles) and they make the tail a little wider at the base in males compared to females.

      We reliably determine sex by probing for the hemipenes. Of course, the snake must be handled for this, which is very dangerous for someone without proper training and experience. It is a simple process done with a smooth blunt probe that’s lubricated and inserted very gently into the pocket on either side of the tail at the cloaca. These pockets lead to a musk gland in both sexes and the probe will only penetrate a few millimeters (maybe 1/8 inch) in females. But in sexually-mature males, it easily penetrates (inside the hemipenis) over half the length of the tail, sometimes nearly 90% of tail length.

      I’m sure that’s more than you wanted to know about rattlesnake anatomy but now you know much more than all your friends!

      Thanks for asking!

      Mike

  2. I work at Effie Yeaw doing landscape work. We occasionally come across small rattlesnakes. I have heard contradictory statements about young rattlesnakes being more dangerous than adults because they have not learned how to control the amount of venom they inject into a bite. Is it true that they are more dangerous?

    1. Hi Trudy,

      Great question! You have asked about the myth that is the most common, by far, concerning rattlesnakes.

      Answer: No! Baby rattlesnakes are not only not more dangerous than big ones, they are less dangerous. Although rattlesnakes never do, let’s assume for a moment that the biting snakes release all of their stored venom. Baby rattlesnakes are the size of pencils when born and weigh about half an ounce. Everything about them is miniature, including the size of their heads and venom glands. Baby rattlesnakes have only a tiny fraction of the venom available to adult rattlesnakes.

      Think about it; laboratories that extract venom from snakes and sell it don’t use small snakes. They want big snakes because they yield a lot more venom per extraction. I often refer to a rather dated publication because it contains a huge amount of data from a Salt Lake City venom lab that’s been in operation for many decades. The reference is: Glenn, J. L., & R. C. Straight. 1982. The rattlesnakes and their venom yield and lethal toxicity. In Tu, A. (editor) Rattlesnake Venoms, Their Actions and Treatment. Published by Marcel Dekker, New York. According to these data, three-foot rattlesnakes yield about 100X the venom of one-foot rattlesnakes (measured by dry weight).

      We also have an excellent paper published out of the Emergency Medicine Department of Loma Linda University Medical Center in southern California regarding clinical severity of rattlesnake bites in people, based on the size of the biting snake. In short, the average severity of bites by medium and large rattlesnakes is about the same (i.e., bigger snakes are slightly higher but within the statistical margin of error). But the average severity of bites produced by small rattlesnakes (estimated at less than 16 inches) is just over half that of the medium and large rattlesnakes. That reference is : Janes D.N., S.P. Bush, & G.R. Kolluru. 2010. Large snake size suggests increased snakebite severity in patients bitten by rattlesnakes in southern California. Wilderness and Environmental Medicine 21:120–126. In other words, it is possible to get a bite with little or no venom injected (called a “dry bite”) from a rattlesnake of any size but people don’t get really severe life- and limb-threatening bites from tiny rattlesnakes. They’re just too small to have much venom, even if they inject a lot of what they have…

      Please spread the word!

      Mike

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